In the Permian, we had true global warming. But it was many, many times of what we have today.
But conditions weren't right, and it has to do with plate tectonics, and simple physics (something alien to geologists!). The plates open and close like toilet seats.
Now, all our earthquakes in eastern NA have their origins in the Precambrian plate closure, when the super continent Rodinia was formed. I love thinking about that, when there were huge mountain ranges over Toronto. Then we'd have some skiing!
But they split, and nothing much happened until they started to join up again before the Permian. It was a time of joy for the early forms of what would eventually become mammals.
But in the Permian, everything joined up to become one big super continent, and here's where the physics comes in. You'll never see this anywhere, but continent was a giant thermal blanket. No spreading ridges between the land masses! Think of all those wet, oceanic subducted plates just baking! The big surprise is that it wasn't the CO2 that turned the whole place into a dinosaur's dreamland, it was the water vapour, which is many times more potent as a greenhouse gas. Can't get volcanic CO2 injection without water vapour, kiddies!
Eventually, the continents split up again, and we got the cold, modern world. Even if you raised a Jurassic dinosaur, you'd have a tough time keeping it alive.